This invention relates to microwave ovens, and especially to such ovens having vertically translatable members, such as resistance heaters, disposed in the heating room thereof.
It is often desirable that a member or members disposed in the heating chamber of microwave ovens and extending therefrom through an opening or openings into the exterior thereof be capable of vertical translation. For example, if the metal sheathed resistance heaters which are disposed in the heating chamber of microwave ovens and extend therefrom into the exterior thereof through the openings defined in the wall of the heating room can be translated vertically, control of the heating intensity to a finer degree becomes possible and higher heating efficiency can be achieved. In the case of conventional microwave ovens in which a rod-shaped heater having a terminal portion thereof extending from the heating chamber into the exterior thereof is rotated around said terminal portion, the rotational range of the heater has been limited. Thus, such conventional microwave ovens have been less than ideal for practical cooking purposes. The above-mentioned advantages resulting from vertically translatable heater may also result from vertically translatable reflectors, partition plates, or supporters for food containers disposed in the heating chamber of microwave ovens and supported by metal rods extending from the heating chamber to the exterior thereof through openings disposed in the walls of the heating chamber. Another case where vertical translation of a member which extends from the interior of the heating chamber of microwave ovens to the exterior thereof through an opening or openings is desirable is the case of temperature or humidity detectors for the foods to be heated which may be disposed in the heating chamber of microwave ovens for detecting to what degree the foods have been cooked. By making detectors capable of vertical translation, it becomes possible to place detector heads into the heated foods and to detect the temperature or the humidity of the foods without interrupting the heating operation, thereby realizing automatic control of the output power of a microwave oven.
In any of these cases, however, it has been practically impossible to make such members as described above vertically translatable, because, for vertical translation of the members disposed in the heating chamber of microwave ovens, one or a plurality of vertically elongated openings must be defined in the walls of the heating chamber through which said members extend from the interior of the heating chamber into the exterior thereof and along the longitudinal direction of which said members are translated vertically, and because there has been no method for preventing the leakage of electromagnetic waves through such elongated openings with practical effectiveness and reliability. This leakage of electromagnetic waves is especially serious because the members extending from the interior of the heating chamber of microwave ovens to the exterior thereof are formed of metal, and such metal members function as antennas which receive and lead out the electromagnetic waves filling the heating chamber of microwave ovens.